1. Field of the Invention
The present invention relates to a light illumination apparatus and a liquid crystal display apparatus using the same.
2. Description of the Prior Art
Liquid crystal display devices having the merit of thinness and low electric power consumption have been applied in recent years to a display system mainly treating motion pictures, such as television receivers, and use thereof is being further enlarged.
Recently, however, there has reported the problem of deterioration of motion picture quality peculiar to hold type display devices represented by liquid crystal display devices (the Institute of Electronics, Information and Communication Engineers (IEICE) Technical Report SID96-4, pp.19-26 (1996-06)). The report also shows that a method of multiplying frame frequency by n, a method in which picture is displayed for 1/n of frame period and black is displayed for the remainder of the frame period, and the like are useful for solving the problem of deterioration of motion picture quality. The effectiveness of these methods for high-speed motion picture display is increased as the value of n increases.
In consideration of the above problem, technical developments corresponding to the quality of motion picture (hereinafter referred to as “motion picture quality”) in liquid crystal display devices have been carried out. As a technology for improving motion picture quality by use of a light illumination apparatus, Japanese Patent Laid-Open No. Sho 64-82019 discloses a motion picture quality improving technology relating to blanking display in which a light-emitting portion of a backlight is blinked in accordance with picture driving scan.
Besides, apart from motion picture quality improving technology, a flat plate type light illumination apparatus providing illumination while changing the optical characteristics of predetermined regions of light-pipes in accordance with display, in order to enhance luminance, has been disclosed in Japanese Patent Laid-Open No. Hei 11-249580.
However, in the technology disclosed in the Japanese Patent Laid-Open No. Sho 64-82019, blanking can be controlled only by the unit of lamp diameter. Namely, blanking cannot be set with optimum timing for each scanning line, and there is still the problem that nonuniformity of luminance is generated between lamps. Although this problem can be solved by increasing the number of lamps, the lamps themselves actually have a diameter of not less than 1.8 mm and, therefore, it is impossible now to carry out blanking with the width on the order of pixels (about several tens of micrometers). Further, the number of lamps and the number of inverters for driving the lamps are extremely increased, which leads to a new problem of high cost.
On the other hand, the light illumination apparatus for illuminating predetermined regions as disclosed in the Japanese Patent Laid-Open No. Hei 11-249580 is useful in the point of concentrating the light incident on light-pipes, but still have problems yet to be solved in order to realize light utility efficiency and uniformity. In addition, the patent publication does not have any description about a driving method corresponding to display of motion picture, so there are still problems to be solved for realizing a light illumination apparatus adapted for motion pictures.